I feel that more specificity is going to be needed in order for you to carve out an effective thesis statement. The best statements of purpose upon which to write a paper are going to be ones that can be substantiated by analysis or critical thought. Most likely, there will be evidence needed to prove the thesis statement. Given these propositions, you will be the only one able to come up with a thesis statement based on what you want to prove and what you have in terms of ideas. The best way to go about this would be to thoroughly examine what it is you have in terms of evidence and thoughts on the issue. For example, are you going to talk about the difficulties in adoption or how the process has changed over time? Are you going to discuss how the social perception of adoption has changed in the last two or three decades? Are you going to discuss statistics regarding adoption? In assessing what you have researched on the topic, the question becomes what you think will make an interesting idea and something that you would like to prove on the issue. Once you are able to determine this, then I think that you will be able to develop a thesis statement that will help you write your paper.